Nope, I don't understand.
Your topic title states (at least that's how I interpret it) that you expect Categories to be blank when you press it (that would be clicking, I guess).
But then you ask why subcategories don't appear ?
First of all there are no subcategories: board > Category > Forum > Subforum
So you probably want to know why subforums are not listed on the index >>> that's a permission setting.
Do you want something like this?